The present disclosure is generally related to colorant compounds. More specifically, the present disclosure is directed to colorant compounds particularly suitable for use in hot melt or phase change inks. In embodiments, the present disclosure is directed to dimeric azo pyrazolone colorant compounds particularly suitable for use in hot melt or phase change inks. One embodiment of the present disclosure is directed to a compound of the formula

and dimers thereof, wherein R and R′ are each independently selected from (i) an alkyl group, (ii) an alkylene group, (iii) an arylene group, (iv) an arylalkylene group, (v) an alkylarylene group, (vi) an alkyleneoxy group, (vii) an aryleneoxy group, (viii) an arylalkyleneoxy group, (ix) an alkylaryleneoxy group, (x) a polyalkyleneoxy group, (xi) a polyaryleneoxy group, (xii) a polyarylalkyleneoxy group, (xiii) a polyalkylaryleneoxy group, (xiv) a heterocyclic group, (xv) a silylene group, (xvi) a siloxane group, (xvii) a polysilylene group, (xviii) a polysiloxane group, or (xix) hydrogen, provided both R and R′ cannot be hydrogen; and
wherein X is a (i) direct bond, (ii) an oxygen atom, (iii) a nitrogen atom, (iv) a sulfur atom, (v) a group of the formula —NR40— wherein R40 is a hydrogen atom, an alkyl group, an aryl group, an arylalkyl group, or an alkylaryl group, (vi) or a group of the formula —CR50R60—; wherein R50 and R60 each, independently of the other, is a hydrogen atom, an alkyl group, an aryl group, an arylalkyl group, or an alkylaryl group; and
wherein (Y)m and (Z)n are each independently optionally present and wherein (Y)m and (Z)n are each independently selected from i) a hydrogen atom, (ii) a halogen atom, (iii) a nitro group, (iv) an alkyl group, (v) an aryl group, (vi) an arylalkyl group, (vii) an alkylaryl group, (viii) a group of the formula

wherein R70 is an alkyl group, an aryl group, an arylalkyl group, an alkylaryl group, an alkoxy group, an aryloxy group, an arylalkyloxy group, an alkylaryloxy group, a polyalkyleneoxy group, a polyaryleneoxy group, a polyarylalkyleneoxy group, a polyalkylaryleneoxy group, a heterocyclic group, a silyl group, a siloxane group, a polysilylene group, or a polysiloxane group, (ix) a sulfonyl group of the formula —SO2R80 wherein R80 is a hydrogen atom, an alkyl group, an aryl group, an arylalkyl group, an alkylaryl group, an alkoxy group, an aryloxy group, an arylalkyloxy group, an alkylaryloxy group, a polyalkyleneoxy group, a polyaryleneoxy group, a polyarylalkyleneoxy group, a polyalkylaryleneoxy group, a heterocyclic group, a silyl group, a siloxane group, a polysilylene group, or a polysiloxane group, or (x) a phosphoryl group of the formula —PO3R90 wherein R90 is a hydrogen atom, an alkyl group, an aryl group, an arylalkyl group, an alkylaryl group, an alkoxy group, an aryloxy group, an arylalkyloxy group, an alkylaryloxy group, a polyalkyleneoxy group, a polyaryleneoxy group, a polyarylalkyleneoxy group, a polyalkylaryleneoxy group, a heterocyclic group, a silyl group, a siloxane group, a polysilylene group, or a polysiloxane group.
and in (Y)m, m is an integer from about 0 to about 4, or about 1 to about 3, or about 1 to about 2, and in (Z)n, n is an integer from about 0 to about 4, or about 1 to about 3, or about 2 to about 3.
In general, phase change inks (sometimes referred to as “hot melt inks”) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops. Phase change inks have also been used in other printing technologies, such as gravure printing, as disclosed in, for example, U.S. Pat. No. 5,496,879 and German Patent Publications DE 4205636AL and DE 4205713AL, the disclosures of each of which are totally incorporated herein by reference.
Phase change inks for color printing typically comprise a phase change ink carrier composition which is combined with a phase change ink compatible colorant. In a specific embodiment, a series of colored phase change inks can be formed by combining ink carrier compositions with compatible subtractive primary colorants. The subtractive primary colored phase change inks can comprise four component dyes, namely, cyan, magenta, yellow and black, although the inks are not limited to these four colors. These subtractive primary colored inks can be formed by using a single dye or a mixture of dyes. For example, magenta can be obtained by using a mixture of Solvent Red Dyes or a composite black can be obtained by mixing several dyes. U.S. Pat. No. 4,889,560, U.S. Pat. No. 4,889,761, and U.S. Pat. No. 5,372,852, the disclosures of each of which are totally incorporated herein by reference, teach that the subtractive primary colorants employed can comprise dyes from the classes of Color Index (C.I.) Solvent Dyes, Disperse Dyes, modified Acid and Direct Dyes, and Basic Dyes. The colorants can also include pigments, as disclosed in, for example, U.S. Pat. No. 5,221,335, the disclosure of which is totally incorporated herein by reference. U.S. Pat. No. 5,621,022, the disclosure of which is totally incorporated herein by reference, discloses the use of a specific class of polymeric dyes in phase change ink compositions.
Phase change inks have also been used for applications such as postal marking, industrial marking, and labeling.
Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and dot quality is improved.
Compositions suitable for use as phase change ink carrier compositions are known. Some representative examples of references disclosing such materials include U.S. Pat. No. 3,653,932, U.S. Pat. No. 4,390,369, U.S. Pat. No. 4,484,948, U.S. Pat. No. 4,684,956, U.S. Pat. No. 4,851,045, U.S. Pat. No. 4,889,560, U.S. Pat. No. 5,006,170, U.S. Pat. No. 5,151,120, U.S. Pat. No. 5,372,852, U.S. Pat. No. 5,496,879, European Patent Publication 0187352, European Patent Publication 0206286, German Patent Publication DE 4205636AL, German Patent Publication DE 4205713AL, and PCT Patent Application WO 94/04619, the disclosures of each of which are totally incorporated herein by reference. Suitable carrier materials can include paraffins, microcrystalline waxes, polyethylene waxes, ester waxes, fatty acids and other waxy materials, fatty amide containing materials, sulfonamide materials, resinous materials made from different natural sources (tall oil rosins and rosin esters, for example), and many synthetic resins, oligomers, polymers, and copolymers.
U.S. Pat. No. 6,576,747 of Rina Carlini et al., entitled “Processes for Preparing Dianthranilate Compounds and Diazopyridone Colorants,” which is hereby incorporated by reference herein in its entirety, discloses a process for preparing dianthranilate compounds which comprises (a) admixing reactants as follows: (1) a diol of the formula R1(OH)2, wherein R1 is an alkylene group having at least about 20 carbon atoms, and wherein the —OH groups are primary or secondary, (2) isatoic anhydride, present in an amount of at least about 2 moles of isatoic anhydride per every one mole of diol, (3) a catalyst which is 1,4-diazabicyclo [2,2,2]octane, N,N,N′,N′-tetramethylethylene diamine, or a mixture thereof, said catalyst being present in an amount of at least about 0.2 mole of catalyst per every one mole of diol, and (4) a solvent; and (b) heating the mixture thus formed to form a dianthranilate compound of the formula

Also disclosed is a process for preparing diazopyridone colorants which comprises (I) preparing a dianthranilate compound by the aforementioned method, (II) reacting the dianthranilate compound with nitrosylsulfuric acid to form a diazonium salt, and (III) reacting the diazonium salt with a pyridine compound to form a diazopyridone compound.
U.S. Pat. No. 6,713,614 of Rina Carlini et al., entitled “Dimeric Azo Pyridone Colorants,” which is hereby incorporated by reference herein in its entirety, discloses compounds of the formula

The compounds are useful as colorants, particularly in applications such as phase change inks.
U.S. Pat. No. 6,663,703 of Bo Wu et al., entitled “Phase Change Inks Containing Dimeric Azo Pyridone Colorants,” which is hereby incorporated by reference herein in its entirety, discloses a phase change ink composition comprising a phase change ink carrier and a colorant compound of the formula

U.S. Pat. No. 6,755,902 of Jeffrey H. Banning et al. entitled “Phase Change Inks Containing Azo Pyridone Colorants” which is hereby incorporated by reference herein in its entirety, discloses a phase change ink composition comprising a phase change ink carrier and a colorant compound of the formula

U.S. Pat. No. 6,590,082 of Jeffrey H. Banning et al. entitled “Azo Pyridone Colorants,” which is hereby incorporated by reference herein in its entirety, discloses compounds of the formula

The compounds are useful as colorants, particularly in applications such as phase change inks.
U.S. Pat. No. 6,696,552 of James D. Mayo et al. entitled “″Process for Preparing Substituted Pyridone Compounds,” which is hereby incorporated by reference herein in its entirety, discloses a process for preparing substituted pyridone compounds which comprises (a) admixing in the absence of a solvent (1) an amine of the formula R1-NH2 wherein R1 is an alkyl group, an aryl group, an arylalkyl group, or an alkylaryl group, and (2) a first ester of the formula

wherein R2 is an electron withdrawing group and R3 is an alkyl group; (b) heating the mixture containing the amine and the first ester to form an intermediate compound of the formula

(c) admixing the intermediate compound with (1) a base and (2) a second ester of the formula

wherein R4 is an alkyl group, an aryl group, an arylalkyl group, or an alkylaryl group and R5 is an alkyl group, said second ester being present in a molar excess relative to the intermediate compound, said base being present in a molar excess relative to the intermediate compound, and (d) heating the mixture containing the intermediate compound, the second ester, and the base to form a pyridone compound of the formula

or a salt thereof. Also disclosed is a process for preparing diazopyridone colorants which comprises preparing a pyridone compound by the above process and reacting the pyridone compound with a diazonium salt to form a diazopyridone compound.
U.S. Pat. No. 6,576,748 of Rina Carlini et al. entitled “Method for Making Dimeric Azo Pyridone Colorants,” which is hereby incorporated by reference herein in its entirety, discloses a process for preparing a diazopyridone compound which comprises (a) preparing a first solution comprising (1) either (A) a dianiline of the formula

or (B) an aniline of the formula

and (2) a first solvent mixture comprising (I) a solvent, (II) acetic acid, and (III) an optional second acid, said acetic acid being present in the solvent mixture in an amount of at least about 95 percent by weight of the solvent mixture, said first solution being at a temperature of about +15° C. or lower; (b) adding to the first solution nitrosylsulfuric acid, thereby forming a diazonium salt either (A) of the formula

or (B) of the formula

(c) preparing a second solution comprising (1) a second solvent mixture comprising water and an organic solvent soluble in or miscible in water, (2) either (A) a pyridone of the formula

or (B) a dipyridone of the formula

(3) a base present in an amount of at least about 3 molar equivalents of base per mole of pyridone moiety, and (4) an optional buffer salt, and (d) combining either (A) the second solution containing the dianiline and the first solution containing the pyridone, or (B) the second solution containing the aniline and the first solution containing the dipyridone to form a third solution and effect a coupling reaction to form a diazopyridone compound either (A) of the formula

or (B) of the formula

U.S. Pat. No. 6,646,111 of Rina Carlini et al. entitled “Dimeric Azo Pyridone Colorants,” which is hereby incorporated by reference herein in its entirety, discloses compounds of the formula

The compounds are useful as colorants, particularly in applications such as phase change inks.
U.S. Pat. No. 6,673,139 of Bo Wu et al. entitled “Phase Change Inks Containing Dimeric Azo Pyridone Colorants,” which is hereby incorporated by reference herein in its entirety, discloses a phase change ink composition comprising a phase change ink carrier and a colorant compound of the formula

While known compositions and processes are suitable for their intended purposes, a need remains for new colorant compositions, for example new yellow to orange colorant compositions. In addition, a need remains for yellow to orange colorant compositions particularly suitable for use in phase change inks. Further, a need remains for yellow to orange colorants with desirable thermal stability. Additionally, a need remains for yellow to orange colorants that exhibit minimal undesirable discoloration when exposed to elevated temperatures. There is also a need for yellow to orange colorants that exhibit a desirable brilliance. In addition, there is a need for yellow to orange colorants that exhibit a desirable hue. Further, there is a need for yellow to orange colorants that are of desirable chroma. Additionally, there is a need for yellow to orange colorants that have desirably high lightfastness characteristics. A need also remains for yellow to orange colorants that have a desirably pleasing color. In addition, a need remains for yellow to orange colorants that exhibit desirable solubility characteristics in phase change ink carrier compositions. Further, a need remains for yellow to orange colorants that enable phase change inks to be jetted at temperatures of over 135° C. while maintaining thermal stability. Further, a need remains for yellow to orange colorants for use in solid ink printers that operate with lower print head temperatures much lower than 135° C. as well as in ultraviolet radiation curable systems. Additionally, a need remains for yellow to orange colorants that enable phase change inks that generate images with low pile height. There is also a need for yellow to orange colorants that enable phase change inks that generate images that approach lithographic thin image quality. In addition, there is a need for yellow to orange colorants that exhibit oxidative stability. Further, there is a need for yellow to orange colorants that do not precipitate from phase change ink carriers. Additionally, there is a need for yellow to orange colorants that do not, when included in phase change inks, diffuse into adjacently printed inks of different colors. A need also remains for yellow to orange colorants that do not leach from media such as phase change ink carriers into tape adhesives, paper, or the like. In addition, a need remains for yellow to orange colorants that, when incorporated into phase change inks, do not lead to clogging of a phase change ink jet printhead. Further, there is a need for yellow to orange colorants that enable phase change inks that generate images with sharp edges that remain sharp over time. Additionally, there is a need for yellow to orange colorants that enable phase change inks that generate images which retain their high image quality in warm climates. Further, there is a need for yellow to orange colorants that enable phase change inks that generate images of desirably high optical density. Additionally, there is a need for yellow to orange colorants that, because of their good solubility in phase change ink carriers, enable the generation of images of low pile height without the loss of desirably high optical density. A need also remains for yellow colorants that enable the use of substantially reduced amounts of colorant in, for example, an ink without decreasing the color and the spectral properties (L*a*b*) of the ink or jeopardizing the optical density or color of the prints generated with the ink. A need also remains for yellow to orange colorants that enable cost-effective inks.
The appropriate components and process aspects of the each of the foregoing may be selected for the present disclosure in embodiments thereof.